Coated paper sheet

Abstract

A coated paper sheet having a coating layer formed on one or two surfaces of a substrate paper sheet and containing a pigment and a binder, wherein the pigment includes kaolin particles having an average particle size of 0.3 to 1.5 μm and an aspect ratio L/W (L: major axis, W: minor axis of the particles) in the range of 5 to 50; the binder contains (a) a copolymer having a glass transition temperature Tg of 10 to 60° C. and a single phase structure and/or a synthetic polymeric compound having a core-shell composite structure; the coating layer surfaces have a 75 degree specular glossiness of 50% or more; and the air permeability of the coated paper sheet is 7000 seconds or less, is useful as printing sheet especially for gravure printing.

1. A coated paper sheet comprising a substrate paper sheet and a coating layer, formed on at least one surface of the substrate paper sheet and comprising a pigment and a binder, wherein,
 the substrate paper sheet is one sizepressed with a sizing agent comprising an oxidized starch;  
 the pigment in the coating layer comprises kaolin particles having an average particle size of 0.3 to 1.5 μm and satisfying the requirement represented by the equation (1): 
   5 ≦L/W ≦16 (1)  
 
 
       wherein L represents a major axis of the kaolin particles and W represents a minor axis of the kaolin particles;
 the binder in the coating layer comprises both (a) a copolymer having a glass transition temperature of 10 to 60° C. and a single phase structure and (b) a synthetic polymeric compound having a core-shell composite structure and satisfying the requirements represented by the inequalities (2) and (3); 
   Tg 1 <Tg 2   (2)  
 
 
       and 
        −10° C. Tg 2 <100° C.  (3) 
       wherein Tg 1  represents a glass transition temperature of a core segment of the synthetic polymeric compound, and Tg 2  represents a glass transition temperature of a shell segment of the synthetic polymeric compound;
 the surface of the coating layer exhibits a 75 degree specular glossiness of 50% or more, determined in accordance with Japanese Industrial Standard Z8741-1997; and  
 the coated paper sheet exhibits an air permeability of 7000 seconds or less, determined in accordance with Japanese Industrial Standard P8117-1998 and a clark stiffness of 12 cm or more in the transverse direction of the coated paper sheet.  
 
     
     
       2. The coated paper sheet as claimed in  claim 1 , wherein the kaolin particles are present in an amount of 30 parts or more by mass per 100 parts by mass of the total amount of the pigment contained in the coating layer. 
     
     
       3. The coated paper sheet as claimed in  claim 1 , wherein the synthetic polymeric compound (b) having the core-shell composite structure and contained, as a binder, in the coating layer is present in an amount of 2 to 25 parts by mass per 100 parts by mass of the total amount of the pigment. 
     
     
       4. The coated paper sheet as claimed in any one of claims  1 ,  2 , or  3 , being one surface-smoothed by a calendering treatment at a calendering roll surface temperature of 80° C. or more.